Digital communication systems include time-division multiple access (TDMA) systems, such as cellular radio communication systems that comply with the GSM telecommunication standard and its enhancements like GSM/EDGE, and code-division multiple access (CDMA) systems, such as cellular radio communication systems that comply with the cdma2000 and wideband CDMA (WCDMA) telecommunication standards. WCDMA is based on direct-sequence spread-spectrum techniques, with pseudo-noise scrambling codes and orthogonal channelization codes separating base stations and physical channels (terminals or users), respectively, in the downlink (base-to-terminal) direction. Digital communication systems also include “blended” TDMA and CDMA systems, such as cellular radio communication systems that comply with the universal mobile telecommunications system (UMTS) standard, which specifies a third generation (3G) mobile system developed by the European Telecommunications Standards Institute (ETSI) within the International Telecommunication Union's (ITU's) IMT-2000 framework. The Third Generation Partnership Project (3GPP) promulgates the UMTS and WCDMA standards.
In WCDMA cellular radio communication systems, 3GPP specifies a cell broadcast short message service (CBS), which enables transmission of unacknowledged messages to all receivers in user equipments (UEs), such as mobile phones, within a cell broadcast area, which can include one or more cells or a geographic area. The duration of a cell broadcast, which is carried by a secondary common control physical channel (S-CCPCH), depends on the type of information broadcast and the information provider. Examples of CBS information are weather information, emergency information, warnings (e.g., of natural disasters), and news reports. CBS messages are cyclically broadcast on a frequency and for a duration agreed with the information provider.
CBS is specified in, for example, 3GPP Technical Specification (TS) 23.041 V10.0.0, Technical Realization of Cell Broadcast Service (CBS) (Release 10) (September 2010), and 3GPP Technical Report (TR) 25.925 V3.5.0, Radio Interface for Broadcast/Multicast Services (Release 99) (December 2004). According to 3GPP TR 25.925, a cell indicates its schedule of CBS messages by higher-layer (i.e., Layers 2 and 3) scheduling. See, e.g., subclauses 6.3.2.2 and 6.3.6.4 of 3GPP TR 25.925.
Various channels, including a primary common control physical channel (P-CCPCH) and the S-CCPCH, between base stations and UEs in a WCDMA system carry physical-layer control signaling (e.g., pilot symbols/signals, transmission power commands, etc.). Clause 6.1 of 3GPP TS 25.211 V10.0.0, Physical Channels and Mapping of Transport Channels onto Physical Channels (FDD) (Release 10) (September 2009) describes the mapping of transport channels on physical channels in a WCDMA communication system. Table 4.1 of 3GPP TR 25.925 indicates that CBS information is carried by the S-CCPCH. It will be appreciated that other communication systems have corresponding channels. Scrambling and channelization codes are well known in the art.
A UE can discover that there is a CBS message available only after the UE demodulates and decodes a paging indicator channel (PICH) that, among other things, indicates to the UE that there may be a CBS message on the S-CCPCH. The UE must demodulate and decode the PICH during every period that the UE has “woken up” its receiver (in a UE's discontinuous reception (DRX) mode of operation) and then demodulate and decode all of the S-CCPCH information in order for the UE to determine if a CBS message is present in the S-CCPCH information.
Demodulation and decoding are processes that require energy, which can be in limited supply in a portable UE like a mobile phone. U.S. Patent Application Publication No. US 2008/0310485 A1 by Soliman et al. (2008 Dec. 18) describes a computer-implemented method that includes identifying available receiver resources and dynamically disabling or enabling subsets of resources based on at least a channel estimation. A signal to interference ratio (SIR), block error rate (BLER), delay spread, and received signal strength indication (RSSI) can also be measured for selecting a number of equalizer fingers, a number of used analog to digital converter bits, and path-searcher monitoring fingers to save power.
European Patent Publication EP 1843492 A1 by Iizuka et al. (2007 Oct. 10) discloses saving power by operating a multi-path interference removing apparatus in a receiver only in a limited number of receiver states, including where the SIR power ration is 8 dB or more.